CONTRIBUTIONS FROM THE ZOai.OGICAL LABOBATOBY OF THE MTI8EDM OF COMP.VBATIVE ZOOLOGY AT 

 HABVABD COLLEGE. NO. 276. 



THE FUNCTION OF THE EFFERENT FIBERS OF THE 

 OPTIC NERVE OF FISHES 



LESLIE B. AREY 



Northwestern University Medical School 



TWELVE FIGURES (tWO PLATES 



CONTENTS 



Preliminary 213 



Statement of the problem 215 



Material and teciinical methods 217 



Experimental part 218 



a. Experimentation upon Ameiurus 218 



1. Retinal pigment 21fl 



2. Visual cells 230 



b. Experimentation upon Abramis and Kundulus 233 



Theorot cal considerations 234 



Summary 239 



Bibliography 240 



PRELIM IN ARY 



A number of observations have been recorded, chiefly upon 

 the frog, which indicate that the retinal pigment and i^isual 

 cells are at least partially under the control of the central nervous 

 system, although the manner and extent of this influence are 

 not well luiderstood. An interrelation between the retinal ele- 

 ments of the two eyes has also been maintained by which stimu- 

 lating agents, such as light or salt crystals, appUed to one retina 

 induce changes^ in the other. It has not only been declared by 



' Extensive experimentation has demonstrated the existence of photomechani- 

 cal responses in the retinal pigment of most of the lower vertebrates. In all 

 cases in which movements of the retinal pigment are demonstrable, light causes 

 an expansion (i.e. a migration toward the external limiting membrane), and dark- 

 ness a contraction of the pigment (figs. 1 and 4). A portion of the cone's inner 

 member, to which the appropriate term 'myoid' has been applied, is also capable 

 of actively shortening when the retina is stimulated by light, a compensatory 



213 



THE JOURNAL OF COMPARATIVE NEUROLOOY, VOL. 26, NO. .3, 

 JUNE, 1916 



